The present invention relates generally to a pressure chamber apparatus and a system or method for compressing workpieces in such an apparatus, and is particularly concerned with a lamination system and method for laminating multi-layer ceramic components.
Pressure can be applied to workpieces by compressing them between opposing metal platens in a press or by placing them in a pressure vessel or chamber. One application of such techniques is in laminating multi-layer ceramic components.
Multi-layer electronic components are typically formed from several layers of ceramic material which are covered with the appropriate printed patterns to form the desired electronic circuit. The layers are first treated to provide a desired pattern of holes of various shapes and sizes, which are then filled with conductive ink or paste. The filled holes are interconnected via an interconnect pattern of conductive ink printed on each layer. The layers are then collated and stacked in precise alignment. The collated stack must then be laminated into a monolithic form through the application of pressure and heat. Under proper conditions, the plastic binder materials soften and flow sufficiently to bond.
If lamination is done by compressing the stacks between opposed heated platens, any cavities in the end product must be filled with a tightly fitting plug or a complex die face must be used. Also, the individual sheets must be cut precisely to uniform dimensions in the blanking process when this technique is used. Another problem with this technique is the difficulty of ensuring even application of pressure over the face of the press.
Where the parts are laminated in a pressure chamber filled with heated water under pressure, other problems arise. In view of the high pressures needed to achieve lamination, typically of the order of 5000 p.s.i., the lid of the pressure chamber is subjected to extremely high forces, equivalent to its area multiplied by the pressure in the chamber, and these forces are all in the same direction, i.e. out of the chamber. It is therefore difficult to provide sufficiently strong closure clamps to restrict movement of a lid subjected to around a million pounds of force, and to adequately seal the chamber under such conditions. This makes the apparatus relatively expensive and also difficult to use. The complex clamps take some time to lock prior to lamination and to release after lamination is completed, so that loading of components and subsequent removal and replacement with a load of new components is a lengthy and tedious procedure. Also, since the pressure chamber is open to the atmosphere at the end of each lamination cycle, air can enter the chamber and must be purged prior to pressurization.